Search

A self-template method is developed for hierarchically yolk-shelled NiCo 2 O 4 spheres (YS-NiCo 2 O 4 ) through a controlled hydrolysis process and followed by a thermal annealing treatment. The yolk-shelled NiCo 2 O 4 spheres possess out-shell consisting of hundreds of ultrathin sheets with 3–5 nm in thickness and solid yolk composing of a large number of nanoparticles. The YS-NiCo 2 O 4 generates a large specific surface area of 169.6 m 2 g −1 . Benefit from the large specific surface area and rich oxygen vacancy, the as-fabricated YS-NiCo 2 O 4 as electrode materials for supercapacitor exhibits high specific capacitance of 835.7 F g −1 at 0.5 A g −1 , an enhanced rate capability and excellent electrochemical stability with 93% retention after 10,000 cycles even at 10 A g −1 . Moreover, a hybrid supercapacitor combined with YS-NiCo 2 O 4 and graphene shows a high energy density of 34.7 Wh kg −1 at the power density of 395.0 W kg −1 at 0.5 A g −1 , even at 20 A g −1 , the hybrid supercapacitor still delivers the energy density of about 12.1 Wh kg −1 and the power density of 11697 W kg −1 . The desirable performance of yolk-shelled NiCo 2 O 4 suggests it to be a promising material as supercapacitor electrodes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Three-dimensionally ordered mesoporous NiCo 2 O x @CeO y was developed by a hard template method. • Ce-doping can effectively adjust the electronic structure and bonding configuration of NiCo 2 O x electrode material. • The hollow cubic structure has high permeability and excellent bearing capacity. • The designed architecture has high specific surface area and abundant paths for electron/ion transport. • The NiCo 2 O x @CeO y //AC exhibits superior activity and stability for asymmetric supercapacitors. From the perspective of nano science and nanotechnology, it is very interesting and important to develop a reasonable and practical synthesis route of nanomaterials for production and life. Here, we develop a strategy of hollow cubic metal oxide nanocages. The method was inspired by Pearson's Hard-Soft-Acid-Base (HSAB) theory, and nanocages with excellent performance were prepared by coordination etching and optimization of reaction conditions. Firstly, Cu 2 O nanocubes were prepared by redox reaction at room temperature. Then, the hollow cubic NiCo 2 O x /CeO y nanocages were obtained by HSAB theory and cerium doping. The nanomaterial has a specific capacitance of up to 1976 F/g at the current density of 1 A/g. In addition, the asymmetric supercapacitor (ASC) prepared with hollow cubic NiCo 2 O x /CeO y nanocage as cathode and active carbon as anode exhibits an energy density as high as 37.1 Wh kg−1 at the power density of 375 W kg−1. The capacitance retention rate of the device is 91.5 % after 10,000 cycles. The device can be charged to light up LED lights. These excellent electrochemical properties, due to their unique structure and synergistic effect between materials, indicate the potential application value of hollow cubic NiCo 2 O x /CeO y nanocages in high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

Porous NiCo 2 S 4 nanosheets derived from bimetallic MOFs directly grow on a conductive substrate as a binder-free electrode. The unique open-structure NiCo 2 S 4 with porosity facilitates the diffusion of electrolyte and possess abundant electroactive sites, which presents a high specific capacity and long-term cycling stability. An assembled hybrid capacitor exhibits the practical performance of high energy density and excellent cycling property. • The porous NiCo 2 S 4 nanosheet arrays derived from bimetallic Metal-organic frameworks derivatives are prepared. • The effect of NiCo 2 S 4 morphology on electrochemical performance and reaction mechanism are discussed. • A hybrid supercapacitor device exhibits high energy density and superior cycling stability. Recently, metal-organic frameworks (MOFs) derived materials in the form of bulk powders with attractive chemical and structural properties show broad application in electrochemical energy storage. Bimetallic materials-based MOFs usually show better electrochemical properties than that of monometallic derivatives, while achieving the bimetallic MOFs-derived materials on current collector as a binder-free electrode is still a challenge. Here we report a new approach to directly obtain a binder-free electrode of bimetallic MOFs-derived NiCo 2 S 4 nanosheet arrays on nickel foam (NF) substrate. The porous NiCo 2 S 4 nanosheet arrays providing fast electrolyte permeation and rich electrochemical active sites, show an excellent specific capacity of 1354.4 C g−1, high rate performance, and outstanding cycling stability of 82.6% retention after 10,000 cycles. A hybrid supercapacitor assembled with the as-obtained binder-free electrode as a cathode and active carbon as an anode, exhibits high energy density of 49.1 Wh kg−1 at a power density of 375 W kg−1 and superior cycling stability of 94.5% retention after 10,000 cycles. These results offer a novel and general approach to construct binder-free electrode materials with advanced performance for the portable and practical energy storage device. [ABSTRACT FROM AUTHOR]